Anatomy of Oral cavity and Pharynx

Dr Mohit GoelJR122 aug. 2012

Oral Cavity2 parts:1] Oral vestibule2]Oral cavity properOral vestibule = slit space between teeth- buccal gingiva and lips-cheek .

>Vestibule communicates with exterior through mouth.

>Size of opening is controlled circumoral muscles such as orbicularis oris, buccinator,depressors and elevators of lips.

ORAL CAVITY PROPER

It is the cavity within the alveolar margins of the maxillae and the mandible

Its Roof is formed by the hard palate anteriorly and the soft palate posteriorly

Its Floor is formed by the mylohyoid muscle. The anterior 2/3rd of the tongue lies on the floor.

hard

soft palate

mylohyoid

FLOOR OF THE MOUTH Covered with mucous

membrane In the midline, a

mucosal fold, the frenulum, connects the tongue to the floor of the mouth

On each side of frenulum a small papilla has the opening of the duct of the submandibular gland

A rounded ridge extending backward & laterally from the papilla is produced by the sublingual gland

NERVE SUPPLY

oSensory Roof: by greater palatine and nasopalatine

nerves (branches of maxillary nerve) Floor: by lingual nerve (branch of

mandibular nerve) Cheek: by buccal nerve (branch of

mandibular nerve)

oMotor Muscle in the cheek (buccinator) and the lip

(orbicularis oris) are supplied by the branches of the facial nerve

MUSCLES

The tongue is composed of two types of muscles:• Intrinsic• Extrinsic

Mylohyoid

The main muscle forming the floor of the mouth is mylohyoid.

GENIOHYOID

Geniohyoid is a narrow muscle which lies above the medial part of . Itarises from the inferior mental spine (genial tubercle) on the back of thesymphysis menti, and runs backwards and slightly downwards to attach to the anterior surface of the body of the hyoid bone.

GenioglossusIt arises from a short tendon attached to the superior genial tubercle behind the mandibular symphysis, above the origin of geniohyoid. From this point itfans out backwards and upwards.

Hyoglossus Hyoglossus is thin and quadrilateral, and arises from the whole length of the greater cornu and the front of the body of the hyoid bone. It passes vertically up to enter the side of the tongue between styloglossus laterally and the inferior longitudinal muscle medially.

Styloglossus

It arises from the anterolateral aspect of the styloid process near its apex

Passing downwards and forwards, it divides at the side of the tongue into a longitudinal part, which enters the tongue dorsolaterally to blend with the inferior longitudinal muscle in front of hyoglossus, and an oblique part, overlapping hyoglossus and decussating with it.

Tip:Submental nodes bilaterally & then deep cervical nodes

Anterior two third:Submandibular unilaterally & then deep cervical nodes

Posterior third:Deep cervical nodes (jugulodigastric mainly)

Lymphatic Drainage

Classification of Neck Nodes According to Levels

Level I

Level II

Level III

Level IV

Level V

Level VI

Level VII

Submental (IA)

Submandibular (IB)

Upper jugular

middle jugular

Lower jugular

Posterior triangle group(Spinal accessory andtransverse cervicalchains)

Prelaryngeal

Pretracheal

Paratrachal

Nodes of upper mediastinum

PHARYNX

Extends from the base of the skull to the lower border of the cricoid cartilage (at which point it border of the cricoid cartilage (at which point it becomes the oesophagus).

Portions of the pharynx lie posterior :• nasal cavity (nasopharynx)• oral cavity (oropharynx)• larynx (laryngopharynx)

NasopharynxRoof : body of sphenoid, basilar part of occipital, bone pharyngeal tonsil Floor: soft palate,pharyngeal isthmus

Anterior wall : post. nasal apertures

Posterior wall: ant. arch of atlas

Lateral wall : auditory tube , tubal elevation , salpingo pharyngeal fold and tubal tonsil

Oropharynx

Roof : soft palate, pharyngeal isthmus

Floor : post. 1/3 tongue, epiglottis, lingual tonsil, median glossoepiglottic fold, 2 lateral glosso epiglottic Fold and vallecula.

Anterior wall : mouth, tongue

Posterior wall : C2,C3

Lateral wall : palatoglossal , palatopharyngeal arches/folds and palatine tonsils

Laryngo pharynx

• Walls:

Ant. – inlet of pharynx Post. – C3 – C6 Lat. – thyroid cartilage

The pharyngeal muscles are a group of muscles that act upon the pharynx.They include:

Inferior constrictor muscle

Middle constrictor muscle

Superior constrictor muscle

Stylopharyngeus muscle

Salpingopharyngeus muscle

Palatopharyngeus muscle

MRI

BUCCINATORMASSETER

INTRINSIC MUSCLE OF TONGUE

GENIOGLOSSUS MYLOHOID

LINGUAL SEPTUMGENIOHYOIDDIGASTRICPLATYSMA

HARD PALATE

TONGUEHYOGLOSSUS M.LINGUAL TONSILSUBMANDIBULAR GLAND

GLOSSOEPIGLOTIC FOLDDIGASTRIC M.PLATYSMA

NASOPHARYNX

PAROTID GLAND

UVULA

PALATINE TONSILDIGASTRIC MUSCLE

SUBMANDIBULAR GLANDPLATYSMA

LATERALPTERYGOIDMEDIAL PTERYGOID

HARD PALATENASOPHARYNX

SUPERIOR CONSTRIC. MSOFT PALATE

INTRINSIC MUSCLE OF TONGUE

MIDDLE CONSTRIC. M.GENIOGLOSSUS

MYLOHOID

OROPHARYNXEPIGLOTIS

HYPOPHARYNXINFERIOR CONSTRICTOR

M.

Buccinator m.Hard palate

Masseter muscleLateral & medial pterygoid

m.Nasopharynx

Longus capitis muscle

Buccinator m.Tongue(genioglossus m.)

Masseter muscleMedial pterygoid m.

Palatine tonsilOropharynx

Longus capitis muscle

Orbicularis orisHyoglossus

GenioglossusMylohoid

OropharynxSubmandibular glandPalatopharyngeus m.

Superior constrictor m.

Orbicularis orisHyoglossus

GenioglossusMylohoidEpiglotis

HypopharynxSubmandibular glandPalatopharyngeus m.Middle constrictor m.

MandibleDigastric m.MylohyoidGeniohyoidHyoid bone

Submandibular glandEpiglotis

HypopharynxPiriform recess

Inferior constrictor m.

SUBLINGUAL SPACEPaired non-fascial lined spaces of oral cavity in deep oral tongue above floor of mouth superomedial to mylohyoid muscle

Communication between sublingual spaces occurs in midline anteriorly as a narrow isthmus beneath frenulum

o SLS communicates with SMS(submandibular space) and inferior para pharyngeal space (PPS) at posterior margin of mylohyoid muscle

• There is no fascia dividing posterior SLS from adjacent SMS.Therefore there is direct communication with SMS and PPS in this location.

Posterior aspect of SLS is divided into medial and lateral compartments by hyoglossal muscle.Clinical Importance• Since neurovascular bundle to tongue travels in SLS,oral cavity SCCa involving posterior SLS is challenging to treat.• If SCCa crosses lingual septum to contralateral SLS, lesion becomes unresectable for cure.

SUBMANDIBULAR SPACE

Fascial-lined space inferolateral to mylohyoid muscle containing submandibular gland, nodes and anterior belly of digastric muscles.SMS is defined as a superficial space above hyoid bone deep to platysma and superficial to mylohyoid sling . Continues inferiorly into infrahyoid neck as anterior cervical space.

Inferolateral to mylohyoid muscle of floor of mouth• Deep to platysma muscle• Cephalad to hyoid bone• "Vertical horseshoe-shaped" space between hyoid bone below and mylohyoid sling above.

• SMS communicates posteriorly with sublingual space and inferior para pharyngeal space at posterior margin of mylohyoid muscle.

• Continues inferiorly into infrahyoid neck as anterior cervical space.

RETROMOLAR TRIGONE

Triangle-shaped area of mucosa posterior to last mandibular molar that covers anterior surface of lower ascending ramus of mandible.

Pterygomandibular raphe (PMR)- Thick fascial band that extends between posterior border of mandibular mylohyoid ridge and hamulus of medial pterygoid plate.It represents thickening of middle layer of deep cervical fascia condensed between posterior margin of buccinator muscle and anterior margin of superior constrictor muscle.

Clinical Importance

• SCCa (squamous cell ca.) of RMT may spread along PMR (Pterygomandibular raphe ).

o Cephalad spread along PMR takes tumor up to inferolateral pterygoid plate- Anteromedial masticator space.

• Tumor is seen at level of inferior pterygoid Plate involving posterior buccinator muscle and anterior superior constrictor muscle.

• Enlarging tumor involves maxillary sinus, Buccal and masticator spaces.

o Caudal spread along PMR takes tumor inferiorly to posterior margin of mylohyoid m.

• Enlarging tumor in this location involves floor of mouth of oral cavity.

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